When to shift a 2004 Boxster S

[Anker]

This is fun.

I am off to a HDPE tomorrow and would like to know the ideal, or close to ideal shift points for maximum acceleration

The information needed to establish this is in the owners manual in the performance graphs in the back.

The first thing is to establish some torque bands using the torque/RPM chart.



I have marked the maximum torque point with a green line, the ideal torque band bracketed with yellow lines and the band you don't want to go outside with red lines.

Why they are placed where they are should be pretty obvious. After 6000 RPM the torque drops off dramatically and I have placed the other red line at the same torque value. The yellow is simply at the torque values half way between the ideal and the red.

The bands are then transferred to the RPM vs speed chart.



So now we have to look at the RPMs to shift at to be at the optimal torque bands.

Starting with first gear I draw a blue line and look for a point where the band between the first gear line and the second gear line sits in the best possible torque band. Because these two gears are spaced pretty far apart you can't avoid falling outside the red band. But we definitely don't want to exceed 6000 RPM, so that's where we shift.

In second gear we can stay inside the red band if we shift at 6000 RPM again. We could shift a tad earlier and possibly get a tiny performance improvement, but 6000 is easy to remember, so that's where I shifted from second to third.

Spacing between third and fourth is close enough to make it easy to stay comfortably inside the yellow band. Shifting at 5250 RPM puts us nicely around the max torque

Exactly the same happens when shifting from fourth to fifth and fifth to sixth at 5250 RPM.

So the answer is simply. When looking for maximum acceleration, upshift from first and second at 6000 RPM and from third, fourth and fifth at 5250 RPM.

Downshifting points also fall out of the same chart. You should downshift from sixth, fifth, fourth and third at roughly 4250 RPM and from second at 3500. I am going to mark 6000, 5350, 4250 and 3500 om my tach with some stickies.

Off to the track.